Surface-treated copper foil, method of producing the surface-treated copper foil, and cooper-clad laminate employing the surface-treated copper foil

ABSTRACT

An object of the invention is to provide a surface-treated copper foil capable of consistently attaining a percent loss of peel strength in resistance against hydrochloric acid degradation of 10% or less as measured on a copper pattern prepared from the copper foil and having a line width of 0.2 mm, by bringing out the maximum effect of the silane coupling agent employed in brass-plated anti-corrosive copper foil. The Another object is to impart excellent moisture resistance to the surface-treated copper foil. In order to attain these objects, the invention provides a surface-treated copper foil for producing printed wiring boards which has been subjected to nodular treatment and anti-corrosion treatment of a surface of a copper foil, wherein the anti-corrosion treatment includes forming a zinc-copper (brass) plating layer on a surface of the copper foil; forming an electrodeposited chromate layer on the zinc-copper (brass) plating layer; forming a silane-coupling-agent-adsorbed layer on the electrodeposited chromate layer; and drying the copper foil for 2-6 seconds such that the copper foil reaches 105° C.-200° C.

TECHNICAL FIELD

[0001] The present invention relates to a surface-treated copper foilwhich has been subjected to anti-corrosion treatment; to a method ofproducing the surface-treated copper foil; and to a copper-clad laminateemploying the surface-treated copper foil.

BACKGROUND ART

[0002] Conventionally, surface-treated copper foil has been employed asa material for producing printed wiring boards, which are widely used inthe electric and electronics industries. In general, surface-treatedcopper foil is bonded, through hot-pressing, onto an electricallyinsulating polymer material substrate such as a glass-epoxy substrate, aphenolic polymer substrate, or polyimide, to thereby form a copper-cladlaminate, and the thus-prepared laminate is used for producing printedwiring boards.

[0003] Particularly, copper foil in which a zinc-copper (brass) platinglayer, serving as an anti-corrosion layer, is formed on a surface of thefoil (hereinafter such copper foil is referred to as “brass-platedanti-corrosive foil”) has been widely employed and exhibits excellentheat resistance characteristics (generally called UL heat resistance)during the manufacture of printed wiring boards. However, it has alsobeen pointed out that brass-plated anti-corrosive copper foil hasdrawbacks such as low resistance to chemicals, particularly tohydrochloric acid. The resistance to hydrochloric acid can be evaluatedthrough the following procedure. In practice, a printed wiring boardhaving a pattern obtained from copper foil is immersed for apredetermined time in a hydrochloric acid solution of predeterminedconcentration. Instead of measuring the amount of the hydrochloric acidsolution which has soaked into an interface between the copper foilpattern and the substrate of the wiring board, the peel strength beforeimmersion and after immersion are measured. The percent loss in peelstrength with respect to the initial peel strength is calculated, andthe value is employed as an index of resistance to hydrochloric acid.

[0004] In general, as the line width of a copper pattern in a printedwiring board decreases, the copper foil for producing a printed wiringboard requires higher resistance to hydrochloric acid. When the copperfoil shows a large loss in peel strength with respect to the initialpeel strength, the interface between the copper foil pattern and thesubstrate readily absorbs a hydrochloric acid solution and the interfacereadily undergoes corrosion. In a printed wiring board produced fromsuch copper foil, the copper circuit pattern is likely to drop out ofthe substrate, since the copper foil is treated with a variety of acidicsolutions during fabrication of printed wiring boards.

[0005] In recent years, the thickness, weight, and dimensions ofelectronic and electric apparatus have been steadily decreasing, andtherefore, there is corresponding demand for further reduction in thewidth of the copper pattern line. In this connection, there isadditional demand for copper foil having higher resistance tohydrochloric acid to be used in the production of printed wiring boards.

[0006] Particularly, regarding brass-plated anti-corrosive foil, avariety of studies have been conducted with the objective of enhancingresistance to hydrochloric acid. For example, Japanese PatentApplication Laid-Open (kokai) No. Hei 04-41696 discloses a method ofsurface-treating a copper foil for producing printed circuits, whichcopper foil has a brass anti-corrosion layer and a chromateanti-corrosion layer in combination. Some references, specified below,disclose methods for enhancing resistance of copper foil to hydrochloricacid, including subjecting a surface to be bonded to a substrate totreatment with a silane coupling agent.

[0007] In a copper-clad laminate, the silane coupling agent is presentbetween a brass anti-corrosion layer formed on metallic copper foil anda substrate formed of any of a variety of organic materials. However,details of the silane coupling agent; e.g., the method of employmentthereof, have not been sufficiently studied. Heretofore, there have beenfiled several patent applications with regard to copper foil employing asilane coupling agent.

[0008] For example, Japanese Patent Publication (kokoku) Nos. Sho60-15654 and Hei 02-19994 disclose copper foil in which a zinc layer orzinc alloy layer is formed on a surface of the foil, a chromate layer isformed on the zinc or zinc alloy layer, and a silane coupling layer isformed on the chromate layer. Judging from consideration of the entiretyof the aforementioned patent publications, these patents focus on dryingtreatment performed after formation of a chromate layer, and treatmentwith a silane coupling agent performed after drying. However, thepresent inventors have found that copper foil of expected performancecannot be obtained when a specific factor is not controlled; i.e.,performance and quality of copper foil, particularly resistance tohydrochloric acid and moisture, vary greatly between lots even when thecopper foil is produced, on a trial basis, by means of the disclosedmethods.

[0009] Japanese Patent Publication (kokoku) No. Hei 02-17950 disclosesthat treatment of copper foil with a silane coupling agent is able toimprove resistance to hydrochloric acid, but does not specificallydisclose the moisture resistance of copper foil. In recent years,problems have arisen which correspond to trends toward formation ofminiature-wiring and multilayer printed wiring boards and in the fieldof packaging of semiconductor devices. Due to the employment of acopper-clad laminate having poor moisture resistance, delamination ofmultilayer printed wiring boards and poor pressure-cooker performance ofpackaged semiconductor devices have occurred.

[0010] Since a silane coupling agent layer is formed on ananti-corrosion layer comprising a zinc or zinc alloy layer formed oncopper foil and a chromate layer formed on the zinc or zinc alloy layer,there arise considerations such as combination of the silane couplingagent and the anti-corrosion layer, surface conditions of theanti-corrosion layer during adsorption of the silane coupling agent, anddrying conditions. Thus, it is considered that no invention which bringsout the maximum effect in the employed silane coupling agent has yetbeen accomplished.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Each of FIGS. 1(a) and 1(b) is a schematic cross-sectional viewshowing the layer structure of surface-treated copper foil.

[0012] Each of FIGS. 2 and 3 is a general schematic cross-sectional viewshowing the constitution of baths included in a surface-treatingapparatus for producing the surface-treated copper foil.

SUMMARY OF THE INVENTION

[0013] The present inventors have attempted to provide surface-treatedcopper foil capable of consistently attaining a resistance againsthydrochloric acid in percent loss of 10% or less as measured on a copperpattern prepared from the copper foil and having a line width of 0.2 mm,by bringing out the maximum effect of the silane coupling agent employedin brass-plated anti-corrosive copper foil. Also, the inventors haveattempted to impart excellent moisture resistance to the surface-treatedcopper foil. Thus, the inventors have conducted extensive studies, andhave found three important factors—i.e., the conditions of theanti-corrosion layer before the copper foil is treated with a couplingagent, which is the most important factor; the timing of treatment withthe silane coupling agent; and drying conditions after treatment withthe silane coupling agent—that must be addressed in order to bring outthe maximum effect of the employed silane coupling agent. The presentinvention has been accomplished on the basis of these findings.

[0014] In claim 1 of the present invention, there is provided asurface-treated copper foil for producing printed wiring boards whichhas been subjected to nodular treatment and anti-corrosion treatment ofa surface of a copper foil, wherein the anti-corrosion treatmentcomprises forming a zinc-copper (brass) plating layer on a surface ofthe copper foil; forming an electrodeposited chromate layer on thezinc-copper (brass) plating layer; forming asilane-coupling-agent-adsorbed layer on the electrodeposited chromatelayer; and drying the copper foil for 2-6 seconds such that the copperfoil reaches 105° C.-200° C.

[0015] In claim 2 of the present invention, there is provided asurface-treated copper foil for producing printed wiring boards whichhas been subjected to nodular treatment and anti-corrosion treatment ofa surface of a copper foil, wherein the nodular treatment comprisesdepositing copper microparticles on a surface of the copper foil; sealplating so as to prevent release of the copper microparticles; andfurther depositing copper ultra-microparticles; and the anti-corrosiontreatment comprises forming a zinc-copper (brass) plating layer on asurface of the copper foil; forming an electrodeposited chromate layeron the zinc-copper (brass) plating layer; forming asilane-coupling-agent-adsorbed layer on the electrodeposited chromatelayer; and drying the copper foil for 2-6 seconds such that the copperfoil reaches a temperature of 105° C.-200° C.

[0016] As shown in FIG. 1, the difference between the surface-treatedcopper foil as recited in claim 1 and that as recited in claim 2 residesin the form of copper microparticles, which provide an anchor effectduring onding to a substrate. Specifically, FIG. 1(a) is a schematiccross-sectional view of a surface-treated copper foil as recited inclaim 1. As shown in FIG. 1(a), on a bulk copper foil surface, coppermicroparticles are formed under conditions for forming burnt deposits,and seal plating is performed so as to prevent release of the coppermicroparticles. During the seal plating, copper is deposited under levelplating conditions. As shown in FIG. 1(b)—a schematic cross-sectionalview of a surface-treated copper foil as recited in claim 29—thestructure is characterized in that copper ultra-microparticles (personsskilled in the art may call the particles “whisker plating”) aredeposited on the seal plating layer of the surface-treated copper foilas recited in claim 1. Typically, the copper ultra-microparticles areformed by use of an arsenic-containing copper plating bath. In FIGS.1(a) and 1(b), an anti-corrosion layer and asilane-coupling-agent-adsorbed layer are not illustrated.

[0017] The surface-treated copper foil as recited in claim 2, in whichcopper ultra-microparticles are formed during a nodular treatment step,is endowed with surface micro-roughness provided by the microparticles,thereby enhancing adhesion to an organic material substrate. Thus, thefoil assures adhesion to a substrate higher than that of thesurface-treated copper foil as recited in claim 1.

[0018] Preferably, the surface-treated copper foil as recited in claim 1is produced through a method as recited in claim 5 or 6. In claim 5,there is provided a method of producing a surface-treated copper foilfor producing printed wiring boards, which method includes asurface-treating method comprising forming a nodular-treated surface ona surface of a copper foil; subjecting the copper foil to anti-corrosiontreatment; effecting adsorption of a silane coupling agent onto thenodular-treated surface; and drying, wherein the anti-corrosiontreatment comprises performing zinc-copper (brass) plating on a surfaceof the copper foil; subsequently performing electrolytic chromatetreatment; drying a surface of the copper foil after electrolyticchromate treatment; effecting adsorption of a silane coupling agent; anddrying the copper foil for 2-6 seconds in a high-temperature atmospheresuch that the copper foil reaches 105° C.-180° C.

[0019] In claim 6, there is provided a method of producing asurface-treated copper foil for producing printed wiring boards, whichmethod includes a surface-treating method comprising forming anodular-treated surface on a surface of a copper foil; subjecting thecopper foil to anti-corrosion treatment; effecting adsorption of asilane coupling agent onto the nodular-treated surface; and drying,wherein the anti-corrosion treatment comprises performing zinc-copper(brass) plating on a surface of the copper foil; subsequently performingelectrolytic chromate treatment; effecting adsorption of a silanecoupling agent without causing the electrolytically chromated surface toattain dryness; and drying the copper foil for 2-6 seconds in ahigh-temperature atmosphere such that the copper foil reaches atemperature of 110° C.-200° C.

[0020] The difference between the method of producing a surface-treatedcopper foil as recited in claim 5 and that as recited in claim 6 residesin the timing for effecting adsorption of silane coupling agent; i.e.,effecting the adsorption treatment after drying of the electricallychromated surface of the copper foil is completed or effecting theadsorption treatment without causing the electrolytically chromatedsurface to attain dryness. The difference will be described hereafterwith reference to experimental data. Actually, surface-treated copperfoil obtained through the latter method; i.e., “a method of producing asurface-treated copper foil including effecting the adsorption treatmentwithout causing the electrolytically chromated surface to attaindryness,” has better quality in terms of resistance to hydrochloricacid.

[0021] Preferably, the surface-treated copper foil as recited in claim 2is produced through a method as recited in claim 7 or 8. In claim 7,there is provided a method of producing a surface-treated copper foil,which method includes a surface-treating method comprising forming anodular-treated surface on a surface of a copper foil; subjecting thecopper foil to anti-corrosion treatment; effecting adsorption of asilane coupling agent onto the nodular-treated surface; and drying,wherein the nodular treatment comprises depositing copper microparticleson a surface of the copper foil; seal plating so as to prevent releaseof the copper microparticles; and further depositing copperultra-microparticles; and the anti-corrosion treatment comprisesperforming zinc-copper (brass) plating on a surface of the copper foil;subsequently performing electrolytic chromate treatment; drying asurface of the copper foil after electrolytic chromate treatment;effecting adsorption of a silane coupling agent; and drying the copperfoil for 2-6 seconds in a high-temperature atmosphere such that thecopper foil reaches a temperature of 105° C.-180° C.

[0022] In claim 8, there is provided a method of producing asurface-treated copper foil, which method includes a surface-treatingmethod comprising forming a nodular-treated surface on a surface of acopper foil; subjecting the copper foil to anti-corrosion treatment;effecting adsorption of a silane coupling agent onto the nodular-treatedsurface; and drying, wherein the nodular treatment comprises depositingcopper microparticles on a surface of the copper foil; seal plating soas to prevent release of the copper microparticles; and furtherdepositing copper ultra-microparticles; and the anti-corrosion treatmentcomprises performing zinc-copper (brass) plating on a surface of thecopper foil; subsequently performing electrolytic chromate treatment;effecting adsorption of a silane coupling agent without causing theelectrolytically chromated surface to attain dryness; and drying thecopper foil for 2-6 seconds in a high-temperature atmosphere such thatthe copper foil reaches 110° C.-200° C.

[0023] Similar to the difference between claims 5 and 6, the differencebetween the method of producing a surface-treated copper foil as recitedin claim 7 and that as recited in claim 8 resides in the timing ofeffecting adsorption of the silane coupling agent; i.e., effecting theadsorption treatment after drying of the electrically chromated surfaceof the copper foil is completed or effecting the adsorption treatmentwithout causing the electrolytically chromated surface to attaindryness. However, claims 5 and 6 differ from claims 7 and 8 in terms oftheir respective nodular treatment steps. Specifically, in claims 5 and6, nodular treatment comprises depositing copper microparticles on asurface of the copper foil and seal plating so as to prevent release ofthe copper microparticles, whereas in claims 7 and 8, modular treatmentfurther comprises depositing copper ultra-microparticles aftercompletion of the seal plating. The difference will be describedhereafter with reference to experimental data. Actually, surface-treatedcopper foil obtained through the latter method; i.e., “a method ofproducing a surface-treated copper foil including effecting theadsorption treatment without causing the electrolytically chromatedsurface to attain dryness,” has better quality in terms of resistance tohydrochloric acid.

[0024] The surface-treated copper foil according to the presentinvention will next be described with reference to claims 5 to 8; i.e.,the method of producing a surface-treated copper foil. Unless otherwisespecified, the conditions for each production step are fixed. Thesurface-treated copper foil according to the present invention isproduced through the following steps: feeding an electrolyte containinga copper component into a space defined by a rotatable drum cathode anda lead anode which faces the cathode so as to surround the rotatablecathode, to thereby effect electrolysis; peeling the resultant thincopper film from the rotatable cathode, to thereby obtain a bulk copperlayer (foil); and subjecting the thus-obtained copper foil tosurface-treatment including nodular treatment, anti-corrosion treatment,and treatment with a silane coupling agent. The bulk copper (foil) mayalternatively be produced from a copper ingot through rolling; i.e., maybe rolled copper foil. Throughout the description, the term “bulk copperlayer (foil)” may be referred to as simply “copper foil,” or, in somecases, may be used as is for the sake of clarity.

[0025] Next, the surface-treatment steps will be described in sequence.The surface-treated copper foil of the present invention is producedthrough surface treatment of copper foil by means of an apparatusgenerally called a surface-treating apparatus. In practice, rolled bulkcopper foil is uncoiled and transferred into a surface-treatmentapparatus in which rinsing baths are appropriately disposed. In theapparatus, the copper foil travels through a pickling bath; a nodulartreatment bath in which copper microparticles are formed on a surface ofthe bulk copper foil; a brass-anti-corrosion bath; anelectrolytic-chromate treatment-anti-corrosion bath; and a dryingsection, which are disposed serially, thereby forming a surface-treatedcopper foil product.

[0026] As shown in FIG. 2—a schematic cross-sectional view of asurface-treating apparatus—uncoiled bulk copper foil travels in awinding manner along the process line (baths and steps) in theapparatus. Alternatively, the surface-treatment may be carried out in abatch manner; i.e., the process line may be segmented.

[0027] In a pickling bath, pickling is carried out in order tocompletely remove oily matter and surface oxide film from bulk copperfoil. The copper foil is passed through the pickling bath so as to cleanthe surfaces and assure uniform electrodeposition carried out in asubsequent step. No particular limitation is imposed on the picklingsolution, and a variety of solutions, such as hydrochloric acidsolution, sulfuric acid solution, and sulfuric acid-hydrogen peroxidesolution, can be employed. The concentration and temperature of thepickling solution may be determined in accordance with characteristicsof the production line.

[0028] After pickling of the bulk copper foil is completed, the copperfoil is transferred into a rinsing bath. Subsequently, the rinsed copperfoil is transferred into a bath for forming copper microparticles on asurface of the bulk copper foil. No particular limitation is imposed onthe electrolyte containing a copper component and employed in the abovebath. However, electrolysis is carried out under conditions for formingburnt deposits so as to deposit copper microparticles. Thus, theconcentration of the electrolyte employed in the above bath fordepositing copper microparticles is adjusted to be lower than that ofthe solution employed in the production of bulk copper foil, so as toreadily attain burnt deposition conditions. The conditions for formingburnt deposits are not particularly limited, and are determined inconsideration of characteristics of the production line. For example,when a copper sulfate solution is employed, the conditions are asfollows: concentration of copper (5-20 g/l), concentration of freesulfuric acid (50-200 g/l), optionally required additives(α-naphthoquinoline, dextrin, glue, thiourea, etc.), solutiontemperature (15-40° C.), and current density (10-50 A/dm²).

[0029] Seal plating is carried out in order to prevent release of thedeposited copper microparticles. The seal plating step involves theuniform deposition of copper such that the copper microparticles arecovered with copper under level-plating conditions in order to preventrelease of the deposited copper microparticles. Thus, the copperelectrolyte employed for performing seal plating has a higherconcentration than does a copper electrolyte employed for depositingcopper microparticles. The seal plating conditions are not particularlylimited, and are determined in consideration of characteristics of theproduction line. For example, when a copper sulfate solution isemployed, the conditions are as follows: concentration of copper (50-80g/l), concentration of free free sulfuric acid (50-150 g/l), solutiontemperature (40-50° C.), and current density (10-50 A/dm²).

[0030] In the method according to claim 7 or 8 for producing asurface-treated copper foil as recited in claim 2, copperultra-microparticles are typically formed by employing an electrolytecontaining a copper component and arsenic. For example, when a coppersulfate solution is employed, the conditions are as follows:concentration of copper (10 g/l), concentration of free free sulfuricacid (100 g/l), concentration of arsenic (1.5 g/l), solution temperature(38° C.), and current density (30 A/dm²).

[0031] In recent years, however, environmental issues have assumedincreasing importance, and insofar as possible, employment of elementswhich pose a hazard to the human body are being eliminated. Accordingly,as recited in claim 9, a copper-component-containing electrolyte towhich 9-phenylacridine is added is employed instead of arsenic. Duringelectrolysis for depositing copper, 9-phenylacridine plays a rolesimilar to that of arsenic. Briefly, 9-phenylacridine enables bothregulation of the size of the copper microparticles deposited anduniform deposition thereof. In order to form copperultra-microparticles, the aforementioned electrolyte contains copper(5-10 g/l), free sulfuric acid (100-120 g/l), and 9-phenylacridine(50-300 mg/l). When electrolysis is carried out by use of theelectrolyte at a liquid temperature of 30-40° C. and a current densityof 20-40 A/dm², stable electrolysis can be performed.

[0032] In the subsequent anti-corrosion bath, treatment to preventoxidation-induced corrosion of a copper foil surface is carried out inaccordance with purposes of use thereof such that, for example, thecopper foil is not affected during production of copper-clad laminatesand printed wiring boards. In the present invention, anti-corrosiontreatment is carried out through the combination of plating of a brasshaving a composition of copper-zinc alloy and electrolytic chromatetreatment.

[0033] When plating of a copper-zinc alloy having a brass composition iscarried out, a plating bath such as a zinc-copper pyrophosphate platingbath or a zinc-copper sulfate plating bath can be employed, since thesolutions of these bathes are chemically stable during long-term storageand exhibit excellent stability to electric current. For example, when azinc-copper pyrophosphate plating bath is employed, plating conditionsare as follows: zinc concentration (2-20 g/l), copper concentration(1-15 g/l), potassium pyrophosphate concentration (70-350 g/l), solutiontemperature (30-60° C.), pH (9-10), current density (3-8 A/dm²) andelectrolysis time (5-15 seconds).

[0034] As recited in claim 3, the copper-zinc brass alloy platingpreferably has a composition of 70-20 wt. % zinc and 30-80 wt. % copper.When a silane coupling agent is brought into adsorption on the brassplating having such a composition and the copper foil is dried under thebelow-mentioned conditions, resistance to hydrochloric acid is mosteffectively attained. This is why the composition is preferred. Inaddition, the brass plating falling within the compositional range caneffectively be formed on a copper foil surface. Thus, this compositionalrange is also suitable from the aspect of product yield.

[0035] After brass plating is completed, the plated copper foil isrinsed. Subsequently, a chromate layer is formed on a surface of therinsed copper foil through electrolysis. Although no particularlimitation is imposed on the electrolysis conditions, preferredconditions are as follows: concentration of chromic acid (3-7 g/l),solution temperature (30-40° C.), pH (10-12), current density (5-8A/dm²), and electrolysis time (5-15 seconds). When chromate treatment iscarried out under the above conditions, a surface of the plated copperfoil is uniformly covered.

[0036] In the method of producing a surface-treated copper foil asrecited in claim 5, the silane-coupling-agent-adsorption treatment iseffected after completion of drying the electrically chromated surfaceof the copper foil. In this case, a drying step is added to the rinsingstep after completion of electrolytic chromate treatment in theprocedure carried out in a surface-treating apparatus. In contrast, inthe method of producing a surface-treated copper foil as recited inclaim 6, the adsorption treatment is effected without causing theelectrolytically chromated and rinsed surface to attain dryness,immediately after completion of formation of the electrodepositedchromate layer.

[0037] In this case, no particular limitation is imposed on the methodfor forming the silane coupling agent layer, and methods such asimmersion, showering, and spraying may be adopted. Any method may beemployed in accordance with production steps, so long as the method canbring the copper foil into contact with a solution containing the silanecoupling agent in the most uniform state.

[0038] As recited in claim 4, any silane coupling agent selected fromamong olefin-group-functional silanes, epoxy-group-functional silanes,acrylic-group-functional silanes, amino-group-functional silanes, andmercapto-group-functional silanes can be employed. When these silanecoupling agents are employed on a copper foil surface to be bonded to asubstrate, it is important that these silane coupling agents exhibit noeffect on a subsequent etching step and the performance of producedprinted wiring boards.

[0039] More specifically, coupling agents employed for glass clothcontained in a prepreg for producing printed wiring boards mayalternatively be used. Examples of such coupling agents includevinyltrimethoxysilane, vinylphenyltrimethoxysilane,γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane,4-glycidylbutyltrimethoxysilane, γ-aminopropyltriethoxysilane,N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane,N-3-(4-(3-aminopropoxy)butoxy)propyl-3-aminopropyltrimethoxysilane,imidazolylsilane, triazinylsilane, and γ-mercaptopropyltrimethoxysilane.

[0040] These silane coupling agents are dissolved in water serving as asolvent so as to attain a concentration of 0.3-15 g/l, and the preparedsolutions are employed at room temperature. The silane coupling agent iscoupled through condensation with OH groups contained in theanti-corrosion layer of the copper foil, to thereby form a coatinglayer. Thus, a coupling agent solution of excessively high concentrationcannot attain coupling effect commensurate with an increase inconcentration, and the concentration should be determined in accordancewith treatment conditions, such as treating machine (line) speed.However, when the concentration is less than 0.3 g/l, adsorption of thesilane coupling agent is slow, thereby failing to attain a typical levelof commercial profitability and failing to attain uniform adsorption. Incontrast, even when the concentration is in excess of 15 g/l, adsorptionrate does not particularly increase and resistance to hydrochloric acidis not particularly enhanced. Such an adsorption condition iseconomically disadvantageous.

[0041] Finally, the drying step is carried out so as to remove water. Inaddition, the step must be carried out so as to accelerate condensationreaction between the adsorbed coupling agent and OH groups contained inthe surface of the anti-corrosion layer and to completely evaporatewater generated during condensation reaction. The drying step cannot becarried out at a temperature that causes breakage or decomposition of afunctional group of the silane coupling agent that forms a bond with aresin constituting a substrate during bonding with the substrate. Thereason for selection of the drying temperature is that adhesion betweencopper foil and the substrate becomes poor when there occurs breakage ordecomposition of the functional group of the silane coupling agent thatforms a bond with a resin constituting a substrate, to thereby fail toattain a maximum effect of the adsorbed silane coupling agent.

[0042] Particularly, copper foil; i.e., metallic material, exhibitsrapid thermal conduction as compared with glassy material or organicmaterial such as plastic to which a silane coupling agent is typicallyapplied. Thus, the silane coupling agent adsorbed on the copper foil issubjected to considerable heat; i.e., high temperature during drying andheat radiated from a heat source. Accordingly, when drying is carriedout by means of a blower; i.e., the temperature of the copper foil iselevated very rapidly by a hot air (gas) supplied from the blower,drying conditions must be determined very carefully. Conventionally,drying has been carried out in consideration of only the temperature ofthe atmosphere or that of the air draft in a drying furnace. However, inthe present invention, the foil is preferably dried by being passedthrough a heating furnace for 2-6 seconds so as to control thetemperature of the foil itself. The reason for a variance in the dryingtime and the drying temperature within certain ranges is that thetemperature elevation rate of copper foil varies due to differences inthe speed at which the surface-treated copper foil is produced orunevenness in the thickness of the copper foil. Thus, operationalconditions are determined within the above ranges in accordance with thetypes of products to be made.

[0043] Among drying conditions, the drying temperature after completionof electrolytic chromate treatment is modified to suit a specificsilane-coupling-agent treatment; i.e., treatment carried out after thebulk copper foil has been dried and treatment carried out withoutcausing the bulk copper foil to attain dryness. The reason for themodification is that the above two types of silane-coupling treatmentdiffer in the temperature range in which functional groups contained inthe silane coupling agent layer formed on the nodular-treated side ofthe substrate and which are bonded to the substrate remain intact,thereby attaining sufficient fixation of the coupling agent to thecopper foil surface.

[0044] In the method of claim 5 or 7, including drying bulk copper foil;treating the dried foil with a silane coupling agent; and further dryingthe treated foil, a considerable amount of heat supplied to thehigh-temperature atmosphere is consumed in condensation reaction of thesilane coupling agent on the chromated layer during the drying. Incontrast, in the method of claim 6 or 8, surface-treated copper foil isproduced by sequentially forming an electrodeposited chromate layer,rinsing, and forming a silane coupling layer without drying the surfaceto which the coupling agent is applied, and subsequently drying. Thus, agreater amount of water remains in the copper foil during drying ascompared with surface-treated copper foil produced by sequentiallyforming an electrodeposited chromate layer, drying, and forming a silanecoupling layer. During heating to dry, a considerable amount of heat isconsumed for evaporating water. Thus, it is assumed that even though thedrying atmosphere temperature is elevated to approximately 200° C., heatsufficient for breaking or decomposing functional groups of the silanecoupling agent is difficult to generate. Thus, breakage of thefunctional groups which are contained in the silane coupling agent layerand which are bonded to the substrate is more effectively prevented,thereby improving the quality of surface-treated copper foil products.

[0045] In order to confirm the assumption, copper foils according toclaim 1 or 2 of the present invention having a thickness of 35 μm wereproduced by drying at various temperatures for four seconds, and each ofthe produced copper foils was laminated with FR-4 to produce acopper-clad laminate. A copper wiring having a line width of 0.2 mm wasformed from the copper-clad laminate, and peel strength was measured foreach laminate. The results of evaluation are shown in Tables 1 to 4.TABLE 1 Peel test results (0.2 mm-line-width circuit) Peel ResistanceMoisture strength to HCl; resistance; Initial after loss in loss in Foilpeel floating on peel peel temperature strength solder bath strengthstrength at drying kg/cm kg/cm (%) (%)  80 1.86 1.85 39.7  20.5  1001.85 1.85 33.8  16.2  105 1.85 1.84 9.9 9.8 110 1.85 1.84 9.7 9.8 1201.87 1.86 8.7 8.5 130 1.86 1.85 9.1 8.2 140 1.87 1.86 7.2 8.3 150 1.871.85 7.6 9.0 160 1.86 1.85 6.9 7.5 170 1.86 1.84 7.3 8.3 180 1.86 1.859.0 7.2 190 1.87 1.86 10.6  11.3  200 1.87 1.86 13.3  10.8  210 1.871.85 19.5  19.8  220 1.86 1.86 23.7  24.6 

[0046] Copper Foil Employed:

[0047] Surface-treated copper foil produced from a copper foil asrecited in claim 1 through a method as recited in claim 5 (no copperultra-microparticles were formed, and silane-coupling-agent treatmentwas carried out after drying).

[0048] Initial Peel Strength:

[0049] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. The peelstrength between the copper line and the substrate was measured.

[0050] Peel Strength After Floating on Solder Bath:

[0051] The copper-patterned board was floated on a solder bath (246° C.)for 20 seconds, and then cooled to room temperature. The peel strengthwas then measured.

[0052] Resistance to HCl (Loss in Peel Strength (%)):

[0053] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. Thethus-prepared board was immersed in a mixture of hydrochloric acid andwater (1:1) for one hour at room temperature, and then removed from themixture, washed with water, and dried. Immediately after the board wasdried, the peel strength was measured. The percent loss in peel strengthwith respect to the initial peel strength was calculated.

[0054] Moisture Resistance (Loss in Peel Strength (%)):

[0055] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. Thethus-prepared board was immersed in boiling ion-exchange water (purewater) for two hours, and then pulled from the water and dried.Immediately after the board was dried, the peel strength was measured.The percent loss in peel strength with respect to the initial peelstrength was calculated. TABLE 2 Peel test results (0.2 mm-line-widthcircuit) Peel Resistance Moisture strength to HCl; resistance; Initialafter loss in loss in Foil peel floating on peel peel temperaturestrength solder bath strength strength at drying kg/cm kg/cm (%) (%)  801.85 1.84 36.6  26.2  100 1.86 1.85 32.7  26.4  105 1.87 1.85 14.5 23.9  110 1.85 1.84 7.5 9.8 120 1.87 1.86 7.9 7.7 130 1.87 1.85 7.2 8.1140 1.87 1.86 6.3 6.5 150 1.86 1.84 7.8 6.7 160 1.85 1.85 7.5 6.0 1701.85 1.84 5.7 8.0 180 1.86 1.85 5.1 8.2 190 1.85 1.84 6.8 9.4 200 1.861.84 7.9 9.6 210 1.87 1.85 14.7  21.8  220 1.85 1.86 23.6  30.3 

[0056] Copper Foil Employed:

[0057] Surface-treated copper foil produced from a copper foil asrecited in claim 1 through a method as recited in claim 6 (no copperultra-microparticles were formed, and silane-coupling agent treatmentwas carried out without causing the copper foil to attain dryness).

[0058] Initial Peel Strength:

[0059] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. The peelstrength between the copper line and the substrate was measured.

[0060] Peel Strength After Floating on Solder Bath:

[0061] The copper-patterned board was floated on a solder bath (246° C.)for 20 seconds, and then cooled to room temperature. The peel strengthwas then measured.

[0062] Resistance to HCl (Loss in Peel Strength (%)):

[0063] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. Thethus-prepared board was immersed in a mixture of hydrochloric acid andwater (1:1) for one hour at room temperature, and then removed from themixture, washed with water, and dried. Immediately after the board wasdried, the peel strength was measured. The percent loss in peel strengthwith respect to the initial peel strength was calculated.

[0064] Moisture Resistance (Loss in Peel Strength (%)):

[0065] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. Thethus-prepared board was immersed in boiling ion-exchange water (purewater) for two hours, and then pulled from the water and dried.Immediately after the board was dried, the peel strength was measured.The percent loss in peel strength with respect to the initial peelstrength was calculated. TABLE 1 Peel test results (0.2 mm-line-widthcircuit) Peel Resistance Moisture strength to HCl; resistance; Initialafter loss in loss in Foil peel floating on peel peel temperaturestrength solder bath strength strength at drying kg/cm kg/cm (%) (%)  801.86 1.85 38.3  29.3  100 1.86 1.85 26.1  17.3  105 1.86 1.84 7.8 6.5110 1.87 1.86 6.8 7.8 120 1.87 1.85 5.2 6.0 130 1.85 1.84 6.6 7.3 1401.87 1.86 5.0 6.7 150 1.86 1.85 5.8 7.2 160 1.88 1.86 6.1 7.6 170 1.871.85 5.8 5.6 180 1.85 1.84 6.9 4.7 190 1.87 1.86 11.8  19.6  200 1.861.86 17.5  20.3  210 1.87 1.85 18.6  25.8  220 1.87 1.86 24.2  26.9 

[0066] Copper Foil Employed:

[0067] Surface-treated copper foil produced from a copper foil asrecited in claim 2 through a method as recited in claim 7 (copperultra-microparticles were formed, and silane-coupling-agent treatmentwas carried out after drying).

[0068] Initial Peel Strength:

[0069] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. The peelstrength between the copper line and the substrate was measured.

[0070] Peel Strength After Floating on Solder Bath:

[0071] The copper-patterned board was floated on a solder bath (246° C.)for 20 seconds, and then cooled to room temperature. The peel strengthwas then measured.

[0072] Resistance to HCl (Loss in Peel Strength (%)):

[0073] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. Thethus-prepared board was immersed in a mixture of hydrochloric acid andwater (1:1) for one hour at room temperature, and then removed from themixture, washed with water, and dried. Immediately after the board wasdried, the peel strength was measured. The percent loss in peel strengthwith respect to the initial peel strength was calculated.

[0074] Moisture Resistance (Loss in Peel Strength (%)):

[0075] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. Thethus-prepared board was immersed in boiling ion-exchange water (purewater) for two hours, and then pulled from the water and dried.Immediately after the board was dried, the peel strength was measured.The percent loss in peel strength with respect to the initial peelstrength was calculated. TABLE 4 Peel test results (0.2 mm-line-widthcircuit) Peel Resistance Moisture strength to HCl; resistance; Initialafter loss in loss in Foil peel floating on peel peel temperaturestrength solder bath strength strength at drying kg/cm kg/cm (%) (%)  801.87 1.85 33.1  28.5  100 1.86 1.85 28.7  27.3  105 1.86 1.84 16.2 22.5  110 1.85 1.84 2.4 9.8 120 1.88 1.86 1.8 7.5 130 1.87 1.85 1.5 8.3140 1.87 1.86 0.6 6.7 150 1.86 1.85 1.3 7.2 160 1.85 1.85 0.0 6.5 1701.86 1.84 1.0 8.3 180 1.86 1.87 0.0 6.0 190 1.87 1.87 1.5 7.1 200 1.881.87 8.9 7.9 210 1.87 1.85 18.6  19.8  220 1.86 1.86 26.8  24.6 

[0076] Copper Foil Employed:

[0077] Surface-treated copper foil produced from a copper foil asrecited in claim 2 through a method as recited in claim 8 (copperultra-microparticles were formed, and silane-coupling agent treatmentwas carried out without causing the copper foil to attain dryness).

[0078] Initial Peel Strength:

[0079] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. The peelstrength between the copper line and the substrate was measured.

[0080] Peel Strength After Floating on Solder Bath:

[0081] The copper-patterned board was floated on a solder bath (246° C.)for 20 seconds, and then cooled to room temperature. The peel strengthwas then measured.

[0082] Resistance to HCl (Loss in Peel Strength (%)):

[0083] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. Thethus-prepared board was immersed in a mixture of hydrochloric acid andwater (1:1) for one hour at room temperature, and then removed from themixture, washed with water, and dried. Immediately after the board wasdried, the peel strength was measured. The percent loss in peel strengthwith respect to the initial peel strength was calculated.

[0084] Moisture Resistance (Loss in Peel Strength (%)):

[0085] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. Thethus-prepared board was immersed in boiling ion-exchange water (purewater) for two hours, and then pulled from the water and dried.Immediately after the board was dried, the peel strength was measured.The percent loss in peel strength with respect to the initial peelstrength was calculated.

[0086] As is clear from Tables 1 to 4, in no specimen is significantdifference observed between initial peel strength and peel strengthafter floating on a solder bath. However, an appropriate dryingtemperature zone is found. The surface-treated copper foil specimenswhich were produced by drying at a temperature falling within thetemperature zone exhibit excellent and constant resistance tohydrochloric acid (loss in peel strength (%)) and moisture resistance(loss in peel strength (%)). Resistance to hydrochloric acid (loss inpeel strength (%)) is an index for showing the loss in peel strengthcaused by treatment with hydrochloric acid as shown in each Table withrespect to the initial peel strength of the copper foil from which acopper pattern was formed, and was calculated from the followingformula:

[0087] [Resistance to hydrochloric acid (loss in peel strength(%))]=([initial peel strength]−[peel strength after treatment withHCl])/[initial peel strength]. Moisture resistance (loss in peelstrength (%)) is an index for showing the loss in peel strength causedby moisture-absorption treatment as described in each Table with respectto the initial peel strength of copper foil from which a copper patternwas formed, and was calculated from the following formula:

[0088] [Moisture resistance (loss in peel strength (%))]=([initial peelstrength]−[peel strength after moisture-absorption treatment])/[initialpeel strength]. Accordingly, the smaller these percent decreases in peelstrength, the better the quality of the surface-treated copper foil.

[0089] In addition, comparison between Tables 1 and 2 and also betweenTables 3 and 4 reveals that the surface-treated copper foil which wasproduced by treating electrically chromated bulk copper foil with asilane coupling agent without causing the copper foil to attain drynesshas better resistance to hydrochloric acid and moisture resistance thando the surface-treated copper foils produced by drying the electricallychromated bulk copper foil and subsequently treating the foil with asilane coupling agent.

[0090] Comparison between Tables 1 and 2 and also between Tables 3 and 4further reveals that when the copper foil was produced by drying bulkcopper foil and subsequently treating the foil with a silane couplingagent, the appropriate temperature of the foil per se at drying (in theTables, the temperature is referred to as foil temperature) falls withinthe range of 105° C. to 180° C. where resistance to hydrochloric acidand moisture resistance are excellent, whereas when the copper foil wasproduced by treating bulk copper foil with a silane coupling agentwithout causing the copper foil to attain dryness, the appropriatetemperature of the foil per se falls within the range of 110° C. to 200°C. where resistance to hydrochloric acid and moisture resistance arefound to be excellent. In the latter case, the foil temperature can beadjusted to a slightly higher temperature than the foil temperature ofthe former case. Thus, it is considered that when the foil temperatureis lower than either lower limit, the silane coupling agent isinsufficiently fixed onto the copper foil, resulting in poor adhesion toa substrate. It is also considered that when the foil temperature is inexcess of either upper limit, the functional groups of the silanecoupling agent that are to be bonded with the substrate are broken ordecomposed, causing poor adhesion to a substrate to thereby lowerresistance to hydrochloric acid and moisture resistance (elevatingdecrease ratios in peel strength).

[0091] Furthermore, comparison between Tables 1 and 3 and also betweenTables 2 and 4 further reveals that the copper foil produced by formingcopper ultra-microparticles after seal plating in nodular treatmentpossesses higher resistance to hydrochloric acid and higher moistureresistance. It is considered that the anchor effect provided by anodular surface of the surface-treated copper foil increases, therebyenhancing adhesion to a substrate.

[0092] As described hereinabove, surface-treated copper foil accordingto the present invention was produced. Copper-clad laminates fabricatedfrom the copper foil produced in the aforementioned manner exhibitexcellent and constant resistance to hydrochloric acid and moistureresistance. Thus, as recited in claim 10, a copper-clad laminateemploying a surface-treated copper foil described in any one of claims 1to 4 has considerably improved quality and provides high reliabilityduring an etching process.

[0093] In the present specification, the term “copper-clad laminate”encompasses a single-sided substrate, a double-sided substrate, and amultilayer substrate. Such substrates may be fabricated from a rigidsubstrate, a hybrid substrate, or a flexible substrate, including aspecially designed substrate such as TAB or COB.

MODES FOR CARRYING OUT THE INVENTION

[0094] Embodiments of the present invention will next be described withreference to FIGS. 1, 2, and 3. In the following embodiments, methods ofproducing surface-treated copper foil 1 according to the presentinvention and copper-clad laminates produced from thethus-surface-treated copper foil 1 are described, along with results ofevaluation. Bulk copper foil 2 employed in the following embodiments iselectrodeposited copper foil.

EXAMPLE 1

[0095] In Example 1, bulk copper foil 2 was surface-treated with asurface-treating apparatus 3. The employed bulk copper foil 2 was coiledbefore surface treatment. In the apparatus 3 shown in FIG. 2, the bulkcopper foil 2 is uncoiled from a foil roll and travels, in a windingmanner, through the surface-treating apparatus 3. Copper foil having anominal thickness of 35 μm and classified as Grade 3 was employed as thebulk copper foil 2, to thereby produce an electrodeposited copper foilemployed in printed wiring boards. Hereinafter, production conditionswill be described with reference to an apparatus wherein a variety ofbaths are continuously disposed in-line. The embodiment will bedescribed with reference to FIG. 1(a) showing a cross-sectional view ofthe surface-treated copper foil.

[0096] Firstly, the copper foil 2 taken from the foil roll wastransferred into a pickling bath 4 filled with a diluted sulfuric acidsolution having a concentration of 150 g/l at 30° C. The foil wasimmersed for 30 seconds, to remove oily matter and surface oxide filmfrom the surface of the bulk copper foil 2.

[0097] After the bulk copper foil 2 had been treated in the picklingbath 4, the foil was transferred into nodular-treatment baths 6 in orderto form copper microparticles 5 on the surface of the bulk copper foil2. The treatment carried out in the nodular-treatment baths 6 involveddepositing copper microparticles 5 on one surface of the bulk copperfoil 2 (step 6A) and seal plating so as to prevent release of the coppermicroparticles 5 (step 6B). In this case, the bulk copper foil 2 itselfwas cathodically polarized, and appropriate anodes 7 were disposed forcarrying out electrolysis. For example, when bulk copper foil 2 issubjected to nodular treatment so as to form double-surface-treatedcopper foil, an anode 7 was disposed to each side of the bulk copperfoil 2.

[0098] Step 6A, depositing copper microparticles 5 on the bulk copperfoil 2, employed a copper sulfate solution (sulfuric acid concentrationof 100 g/l, copper concentration of 18 g/l, temperature 25° C.), andelectrolysis was carried out for 10 seconds under conditions for formingburnt deposits at a current density of 10 A/dm². In this case, as shownin FIG. 2, anode plates 7 were placed such that the anode plates faced,in parallel, the surface of the bulk copper foil 2, onto which coppermicroparticles 5 are formed.

[0099] Step 6B, seal plating so as to prevent release of the coppermicroparticles 5, employed a copper sulfate solution (sulfuric acidconcentration of 150 g/l, copper concentration of 65 g/l, temperature45° C.), and electrolysis was carried out for 20 seconds under uniformplating conditions and at a current density of 15 A/dm², to thereby forma seal plating layer 8. In this case, as shown in FIG. 2, anode plates 7were placed such that the anode plates faced, in parallel, thecopper-microparticles (5)-deposited surface of the bulk copper foil 2.The anodes 7 were formed of stainless steel plates.

[0100] Anti-corrosion treatment through brass plating was carried out ina brass-anti-corrosion-treatment bath 9, by use of zinc-copper alloy asa corrosion-inhibitor. The zinc concentration in thebrass-anti-corrosion-treatment bath 9 was maintained by employing anodes7 as shown in FIG. 2. The electrolysis was carried out in aconcentration-maintained zinc sulfate solution comprising free sulfuricacid (70 g/l) and zinc (20 g/l), at a temperature of 40° C. for eightseconds and at a current density of 15 A/dm².

[0101] Anti-corrosion treatment through electrolytic chromate treatmentwas carried out in a chromate treatment-anti-corrosion-treatment bath10, to thereby electrolytically form a chromate layer on thebrass-plated anti-corrosion layer formed in the brass-anti-corrosiontreatment bath 9. The electrolysis was carried out in a solutioncomprising chromic acid (5.0 g/l), at 35° C. and a pH of 11.5 for fiveseconds and at a current density of 8 A/dm². In this case, as shown inFIG. 2, anode plates 7 were placed such that the anode plates faced, inparallel, the surface of the copper foil.

[0102] After completion of the anti-corrosion treatment, the copper foilwas rinsed with water, and immediately and without drying the surface ofthe copper foil, adsorption of a silane coupling agent on theanti-corrosion layer of the nodular-treated side was effected in asilane-coupling-agent-treatment bath 11. The employed solution wasformed of γ-glycidoxypropyltrimethoxysilane (5 g/l) dissolved inion-exchange water. The solution was sprayed onto the copper foilsurface through showering.

[0103] After completion of the silane-coupling-agent treatment, thecopper foil 2 was passed through, over 4 seconds, a heated furnaceincluding a drying section 12 where the atmosphere had been adjusted bymeans of an electric heater 13 so as to attain a foil temperature of150° C., to thereby accelerate condensation reaction of the silanecoupling agent. The thus-dehydrated surface-treated copper foil 1 wasthen wound into a roll. During the aforementioned steps, the bulk copperfoil ran at 2.0 m/minute. A rinsing bath 14 capable of performing about15 sec. water-rinsing was optionally disposed between successiveoperation baths, thereby preventing the solution from being carried overfrom the previous bath.

[0104] The thus-formed surface-treated copper foil 1 and two sheets ofFR-4 prepreg, serving as substrates and having a thickness of 150 μm,were laminated to thereby produce a double-sided copper-clad laminate.The peel strength at the bond interface between the surface-treatedcopper foil 1 and the substrate was measured. The measurement wascarried out at three points per specimen, and the results are shown inTable 5.

EXAMPLE 2

[0105] In Example 2, bulk copper foil 2 was surface-treated with asurface-treating apparatus 3. The employed bulk copper foil 2 was coiledbefore surface treatment. In the apparatus 3 shown in FIG. 3, bulkcopper foil 2 is uncoiled from a foil roll and travels, in a windingmanner, in the surface-treating apparatus 3. Copper foil having anominal thickness of 35 μm and classified as Grade 3 was employed as thebulk copper foil 2, to thereby produce an electrodeposited copper foilemployed in printed wiring boards. Hereinafter, production conditionswill be described with reference to an apparatus wherein a variety ofbaths are continuously disposed in-line. In order to avoid redundantdescription, only portions that differ from corresponding portionsdescribed in relation to Example 1 will be described. Portions identicalwith those of Example 1 are denoted by the same reference numerals inFIG. 3, so far as such is possible. The embodiment will be describedwith reference to FIG. 1(b) showing a cross-sectional view of thesurface-treated copper foil.

[0106] The flow of surface treatment carried out in Example 2 isidentical with that carried out in Example 1, except that the nodulartreatment carried out in baths 6 comprises three steps; i.e., step 6Afor depositing copper microparticles 5; seal plating step 6B; and step6C for depositing copper ultra-microparticles 15. Briefly, the step 6Cfor depositing copper ultra-microparticles 15 is disposed between theseal plating step 6B, as carried out in Example 1, and thebrass-anti-corrosion step carried out in the bath 9.

[0107] Step 6C, depositing copper ultra-microparticles 15, employs acopper sulfate solution (copper concentration of 10 g/l, sulfuric acidconcentration of 100 g/l, 9-phenylacridine concentration of 140 mg/l,temperature 38° C.), and electrolysis was carried out at a currentdensity of 30 A/dm². Other conditions of treatment steps carried out inthe baths are identical with those employed in Example 1.

[0108] The thus-formed surface-treated copper foil 1 and two sheets ofFR-4 prepreg, serving as substrates and having a thickness of 150 μm,were laminated to thereby produce a double-sided copper-clad laminate.The peel strength at the bond interface between the surface-treatedcopper foil 1 and the substrate was measured. The measurement wascarried out at three points per specimen, and the results of Examples 1and 2 are shown in Table 5. TABLE 5 Peel test results (0.2 mm-line-widthcircuit) Peel Resistance Moisture strength to HCl; resistance; Initialafter loss in loss in peel floating on peel peel strength solder bathstrength strength Specimens kg/cm kg/cm (%) (%) Example 1 1 1.83 1.813.8 9.5 2 1.85 1.84 4.3 8.7 3 1.83 1.83 2.1 7.7 4 1.85 1.83 3.3 9.1 51.84 1.82 3.7 8.9 6 1.86 1.85 2.6 9.6 7 1.83 1.84 2.7 8.4 Example 2 11.87 1.85 0.8 7.8 2 1.86 1.84 1.5 9.0 3 1.86 1.85 0.0 6.5 4 1.85 1.841.0 8.7 5 1.88 1.86 0.0 9.6 6 1.87 1.87 0.4 8.3 7 1.86 1.84 1.2 6.8

[0109] Initial Peel Strength:

[0110] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. The peelstrength between the copper line and the substrate was measured.

[0111] Peel Strength After Floating on Solder Bath:

[0112] The copper-patterned board was floated on a solder bath (246° C.)for 20 seconds, and then cooled to room temperature. The peel strengthwas then measured.

[0113] Resistance to HCl (Loss in Peel Strength (%)):

[0114] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. Thethus-prepared board was immersed in a mixture of hydrochloric acid andwater (1:1) for one hour at room temperature, and then removed from themixture, washed, and dried. Immediately after the board was dried, thepeel strength was measured. The percent loss in peel strength withrespect to the initial peel strength was calculated.

[0115] Moisture Resistance (Loss in Peel Strength (%)):

[0116] A copper-clad laminate was prepared from FR-4, and a copperpattern having a line width of 0.2 mm was formed on FR-4. Thethus-prepared board was immersed in boiling ion-exchange water (purewater) for two hours, and then pulled from the water and dried.Immediately after the board was dried, the peel strength was measured.The percent loss in peel strength with respect to the initial peelstrength was calculated.

[0117] As is clear from the results shown in Table 5, copper patternsobtained from the surface-treated copper foil 1 produced in Example 1 or2 attained a resistance to hydrochloric acid and a moisture resistanceof 10% or less, even through the line width of the patterns was 0.2 mm.Particularly, the resistance to hydrochloric acid was 5% or less, whichis remarkably excellent. Interlot variation in resistance tohydrochloric acid and in moisture resistance investigated for at least10 lots of copper-laminated products obtained in a manner similar tothat of Example 1 or 2 was considerably small. Thus, the copper foil ofthe present invention has a high and stable quality which has never beenattained, as compared with conventional copper foil, and can drasticallyenhance the quality of printed wiring boards.

EFFECTS OF THE INVENTION

[0118] By employing the surface-treated copper foil of the presentinvention, drastically enhanced reliability in adhesion of acopper-foil-derived circuit to a substrate in printed wiring boardsduring an etching step is obtained; a variety of methods for processingprinted wiring boards can be applied; and control of production stepsbecomes easier. In addition, the method of the present invention forproducing the surface-treated copper foil can provide a surface-treatedcopper foil exhibiting excellent resistance to hydrochloric acid andmoisture resistance by bringing out the maximum effect of the silanecoupling agent adsorbed onto the copper foil.

1. A surface-treated copper foil for producing printed wiring boardswhich has been subjected to nodular treatment and anti-corrosiontreatment of a surface of a copper foil, wherein the anti-corrosiontreatment comprises forming a zinc-copper (brass) plating layer on asurface of the copper foil; forming an electrodeposited chromate layeron the zinc-copper (brass) plating layer; forming asilane-coupling-agent-adsorbed layer on the electrodeposited chromatelayer; and drying the copper foil for 2-6 seconds such that thetemperature of the copper foil reaches 105° C.-200° C.
 2. Asurface-treated copper foil for producing printed wiring boards whichhas been subjected to nodular treatment and anti-corrosion treatment ofa surface of a copper foil, wherein the nodular treatment comprisesdepositing copper microparticles on a surface of the copper foil; sealplating so as to prevent release of the copper microparticles; andfurther depositing copper ultra-microparticles, and the anti-corrosiontreatment comprises forming a zinc-copper (brass) plating layer on asurface of the copper foil; forming an electrodeposited chromate layeron the zinc-copper (brass) plating layer; forming asilane-coupling-agent-adsorbed layer on the electrodeposited chromatelayer; and drying the copper foil for 2-6 seconds such that thetemperature of the copper foil reaches 105° C.-200° C.
 3. Asurface-treated copper foil according to claim 1 or 2 , wherein thebrass plating comprises 70-20 wt. % zinc and 30-80 wt. % copper.
 4. Asurface-treated copper foil according to any one of claims 1 to 3 ,wherein a silane selected from among olefin-group-functional silanes,epoxy-group-functional silanes, acrylic-group-functional silanes,amino-group-functional silanes, and mercapto-group-functional silanes isemployed as the silane coupling agent.
 5. A method of producing asurface-treated copper foil as recited in any one of claims 1, 3 and 4for producing printed wiring boards, which method includes asurface-treating method comprising forming a nodular-treated surface ona surface of a copper foil; subjecting the copper foil to anti-corrosiontreatment; effecting adsorption of a silane coupling agent onto thenodular-treated surface; and drying, wherein the anti-corrosiontreatment comprises performing zinc-copper (brass) plating on a surfaceof the copper foil; subsequently performing electrolytic chromatetreatment; drying a surface of the copper foil after electrolyticchromate treatment; effecting adsorption of a silane coupling agent; anddrying the copper foil for 2-6 seconds in a high-temperature atmospherein which the temperature of the copper foil reaches 105° C.-180° C.
 6. Amethod of producing a surface-treated copper foil as recited in any oneof claims 1, 3 and 4 for producing printed wiring boards, which methodincludes a surface-treating method comprising forming a nodular-treatedsurface on a surface of a copper foil; subjecting the copper foil toanti-corrosion treatment; effecting adsorption of a silane couplingagent onto the nodular-treated surface; and drying, wherein theanti-corrosion treatment comprises performing zinc-copper (brass)plating on a surface of the copper foil; subsequently performingelectrolytic chromate treatment; effecting adsorption of a silanecoupling agent without causing the electrolytically chromated surface toattain dryness; and drying the copper foil for 2-6 seconds in ahigh-temperature atmosphere in which the temperature of the copper foilreaches 110° C.-200° C.
 7. A method of producing a surface-treatedcopper foil as recited in any one of claims 2 to 4 , which methodincludes a surface-treating method comprising forming a nodular-treatedsurface on a surface of a copper foil; subjecting the copper foil toanti-corrosion treatment; effecting adsorption of a silane couplingagent onto the nodular-treated surface; and drying, wherein the nodulartreatment comprises depositing copper microparticles on a surface of thecopper foil; seal plating so as to prevent release of the coppermicroparticles; and further depositing copper ultra-microparticles, andthe anti-corrosion treatment comprises performing zinc-copper (brass)plating on a surface of the copper foil; subsequently performingelectrolytic chromate treatment; drying a surface of the copper foilafter electrolytic chromate treatment; effecting adsorption of a silanecoupling agent; and drying the copper foil for 2-6 seconds in ahigh-temperature atmosphere in which the temperature of the copper foilreaches 105° C.-180° C.
 8. A method of producing a surface-treatedcopper foil as recited in any one of claims 2 to 4 , which methodincludes a surface-treating method comprising forming a nodular-treatedsurface on a surface of a copper foil; subjecting the copper foil toanti-corrosion treatment; effecting adsorption of a silane couplingagent onto the nodular-treated surface; and drying, wherein the nodulartreatment comprises depositing copper microparticles on a surface of thecopper foil; seal plating so as to prevent release of the coppermicroparticles; and further depositing copper ultra-microparticles, andthe anti-corrosion treatment comprises performing zinc-copper (brass)plating on a surface of the copper foil; subsequently performingelectrolytic chromate treatment; effecting adsorption of a silanecoupling agent without causing the electrolytically chromated surface toattain dryness; and drying the copper foil for 2-6 seconds in ahigh-temperature atmosphere in which the temperature of the copper foilreaches 110° C.-200° C.
 9. A method of producing a surface-treatedcopper foil according to claim 7 or 8 , wherein copperultra-microparticles are formed from a copper-component-containingelectrolyte to which 9-phenylacridine is added.
 10. A copper-cladlaminate prepared by employing a surface-treated copper foil as recitedin any one of claims 1 to 4 .